How to animate a mask with interval steps and not consecutive flow animation
At last, a use for the Build modifier?
Create a fan-filled circle-mask with the same number of segments as you have LEDs, rotate in Z to the desired start-point. Give it a Build modifier, set to the appropriate frame start/end, and 'Reverse'.

Segments are made visible one at a time.
@blender breath Thanks for the comment.. 'mask' is a bit vague - it could be so many things..

For a 3D mask, as you have done, assign a Solidify modifier to the circle, to get a cylinder disappearing in chunks, which can be used in a Boolean to cut away the LEDs
2D, a perfectly black Diffuse BSDF mask in a black world,
Or, as here, 2D, a Holdout mask through to transparent film, composited against a coloured background -

or, I'm sure, many other possibilities, for use in compositing, or as a texture.